The present invention relates to color television receivers and more particularly to color television receivers having at least one digital integrated circuit for processing the composite color signal.
Color television receivers of this kind are described in German Patent DE-OS No. 2,854,236, and the composite color signal is regenerated therein by all-digital circuitry. To accomplish this, the color television receiver contains a square wave clock generator employed as a chrominance subcarrier oscillator for generating at least four clock signals. The first clock signal has a frequency four times the chrominance subcarrier frequency, while the three remaining clock signals have a frequency equal to the chrominance subcarrier frequency, with the first and second clock signals having a 1:1 mark/space ratio. The above-mentioned color television receiver further includes a stage providing the digital chrominance signal and a parallel multiplier whose two input signals are the digital chrominance signal and a digital chroma control signal.
In circuits of color television receivers using analog signal regeneration, the amplitude of the received chrominance subcarrier wave, which is contained in the so-called burst, is commonly maintained at the constant value. Such receivers contain a stage which determines whether the transmitted signal is a signal transmitted according to the PAL standard or not, in which latter case this signal is used for color killing, see for instance, the book by O. Limann, "Fernsehtechnik ohne Ballast," 12th edition, Munich 1978, pages 209 to 211, 220 and 221.